This proposal is designed to study a) the mechanism of the conformational change of hemoglobin by utilizing hemoglobin variants, ENDOR spectra, mixed liganded hybrids,b) the interaction of hemoglobin with the red cell membrane utilizing hemoglobin variants, surface tension determinations and various electrophoretic methods, c) the hemoglobin-haptoglobin reaction using animal hemoglobins and chemically modified hemoglobins, d) the polymerization of hemoglobin S using hemoglobin variants, modified hemoglobins and hybrids.